| Bacterial wilt, a severe and devastating plant disease caused by Ralstoniasolanacearum, occurs widely in tropical, subtropical, warm temperate areas, evensome cool regions and widely affects lots of plants, especially potatoes and tomatoes.It has been proved that the most efficient, economical way to control plant disease isthe use of resistant varieties. To date, the resistant genes to bacterial wilt allmost havenot been found in potato cultivars (Solanum tuberosum L., 2n=4x=48), and becauseof cross barrier between diffirent ploidy in potatos, somatic hybridization has beenperformed. At present, some somatic hybrids have been successfully obtained bysomatic hybridization between wildtype diploid species (Solanum chacoense, 2n=2x=24), contained resistant genes, and tetraploid potato cultivar clones 3#, 8# (2n=4x=48) from 'Zhongshu 2' (S.tuberosum L.). The purposes of this research are to conformploidy of somatic hybrids, and provide an approch to controll bacterial wilt.The mainresults are as follows:Through root/shoot tip slide method, we have totally counted chromosomenumber of 3 parents (S. chacoense, 3# and 8#) and 60 somatic hybrids. In totalsomatic hybrids, 25 of 60 somatic hybrids were from 3# + S. chacoense, termed3c-serial, and the left from 8# + S. chacoense were named 8c-serial. The countingresult compared with that of flow cytometry revealed that 37 somatic hybrids ploidywere 6x detected by flow cytometry, while 36 hybrids showed same result bychromosome counting, only one somatic hybrid (3c12-2) was found to be complexploidy. In 6 8x ploidy somatic hybrids detected by flow cytometry, only 3c32-1showed the same result by chromosome counting, and the other 5 somatic hybrids(3c10-1, 3c25-3, 8c57-2, 8c60-1, 8c65-1) were all complex ploidy. In 13 complexploidy somatic hybrids by flow cytometry, 8 hybrids (3c4-1, 3c39-1, 8c13-2, 8c15-1,8c34-1, 8c36-2, 8c48-1, 8c66-1) were also complex ploidy, however, two (3c3-7,8c2-2) of five somatic hybrids were 6x, somatic hybrids 3c34-1 and 8c17-3 were 5x,and the left one was 7x/8x mosaic by chromosome counting.During continuous two years experiments in the open field and plastic net tunnel,we recorded the plant height, leaf shape index, stolon length and stem diameter of 131somatic hybrids. It showed that the stolon length was the biggest variable coefficient,which was 118.16, leaf shape index was the smallest variable coefficient, only about9.80, and the variable coefficients of plant height and stem diameter were betweenthem. Most somatic hybrid plants growed normally, but shorter and slimmer than their parents, 8x or complex ploidy somatic hybrids growed abnomally. Wrinkled leavesand flowers happened to be in group of 6x plants, all the 8x and complex ploidyplants. 115 of 131 somatic hybrids, acounting 87.8%, formed tuber, and 35 somatichybrids, 26.7% in total, blossomed. The flower shape of somatic hybrid was gradeddistribution between parents, and the fllower colour from white to purple. Stolonlength was skewed distribution which showed more similarity to that of the cultivarparents. In addition potato peel was the same color as the parents (yellow), fewshowed purple. Seaval hybrids tuber showed unhealthy phenotype such as break androt in the surface or irregularity shape.
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